Aerospikes on Transonic Wings

Abstract

During flights at high velocities, locally, a supersonic flow regime is formed above wings. The supersonic flow is terminated by a shock wave. This happens especially under off-design flight conditions and results in a wave drag. In addition, the shock-boundary layer interaction can cause a separation of the boundary layer and can thus lead to further losses and, eventually, to buffeting. These phenomena limit the maximum economic cruise speed of airplanes. The negative effect of the transonic flow regime can be mitigated by controlling the shock terminating the supersonic region above the wing. Normally, this is achieved by means of passive ventilation (perforated plates, slots, grooves), active suction, contour bumps or by adaptive walls. These approaches have in common that measures for controlling the shock are applied directly at the surface of the wing. However, a control of the shock wave is also possible by external devices placed above the surface of the wing in the supersonic flow regime. The latter concept is related to the one of aerospikes on blunt bodies. In a preliminary test series the effectiveness of a variety of different spike-shaped bodies placed above a transonic wing was tested in the DNW-TWG, Göttingen. In addition to pressure measurements a colour schlieren system was set up for providing information about the influence of spikes on the flow field.